Of course they can, though not as easily as you seem to think I suspect. Radar technology is very secret. Regardless, it’s a matter of numbers. I’m sure the Ukranians would love to field unlimited predator drones if they could. In reality, they field DJI and other commercial drones en masse because of availability. Only relatively recently have they got their own cheap mass produced drones online. These drones are also easier to destroy than a predator, so by your logic, why would they have invested in this? Wunderwaffe never wins wars, logistics do.